Sunpower 435W panels. As mentioned they have a higher voltage.
Are micro invertors the future of residential installations?
- Thread starter Noho
- Start date
fromport
Solar Addict
Ahh commercial panels, and you are using those for residential. Out there in the solar fields there is no requirement for RSD etc so these are all made for (3 phase) high power hight voltage string inverters.
Ampster
Renewable Energy Hobbyist
I have used some of those. mine required a micro inverter for 96 cell panels ut other than that the DC is the same. I have others in a string on a hybrid inverter. Mine were earlier 305 Watt models.
A friend has some iQ7(X?) for the 96 cell panels (he's actually selling them). I looked at the specs to see if I could use them myself, but the VOC on these panels is still too high, especially in the winter months where it could potentially reach 94V at my location.
Ampster
Renewable Energy Hobbyist
I think I uaed IQ7 plus. I could not find any used ones so I bought 4 new ones,
Would you use microinverters on an install with no grid sellback? Say AC Coupled with hybrid inverter doing frequency shifting?
I just checked and the iQ7+ only goes up to 60V, the iQ7X (for 96 cell panels) goes up to 79.5V, still well below the adjusted VOC on my panels. My guess is you were using the iQ7X and either your panels had a lower VOC, or those micros are underrated. If the later, it might be worth a try seeing if those micros my friend has might work for my panels.
Edit: I just looked and I'm guessing you were using these SP 305W lower 96 cell panels.
Last edited:
This is where my interest is as well, maybe tying them in with a SA.
fromport
Solar Addict
Btwafter a "rapid shutdown" on a residential building, all voltages should be below 80 volts within 30 seconds.
That is why you will not see micro inverters that will accept higher than 80 volts
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
- Messages
- 19,930
I'm thinking about building my own EV. So that I can have double duty on the battery bank. I think that it would be easier to make everything work together, if I build it myself. EV battery will charge from solar and double as backup storage for house. It's still a bit in the future. So, I have plenty of time to work out the design details.
Which makes me wonder, if not strongly consider if a micro (such as the iQ7X which is rated at 79.5V max) is artificially underrated. I spoke to one optimizer mfg and they told me their product is only rated to 80V to stay under for NEC RS requirements, but stated they have no problem up to around 100V before they start running into issues. I might buy one of those iQ7X off my buddy and put it to the test when the weather cools off.
ncsolarelectric
Engineering Support CEO
Unfortunately, the National Fire Protection Authority has added more complexity. If you put solar panels on your roof, code requires a means of Rapid Shutdown if there are string voltages over 80V.
ncsolarelectric
Engineering Support CEO
I am anxious to test it. The Hoymiles inverters, when coupled with their meter and DTU-Pro can limit the export to 0kW. However, it has not been tested on a microgrid (yet). Its intent is to manage export to the grid and to control VARs.
Also, I'm not sure how one "gets away" with connecting a grid-tied inverter like a Sol-Ark and setting it for 0 export. I've done 0 export utility-scale systems and even though there was no export, the utility required lots of hardware to assure that was the case and SCADA to monitor that nothing was being back-fed. A lot of people are installing Sol-Arks which are grid-tied utility-interactive inverters. Do the utilities just "take it on faith and goodwill" that their inverter is not going to backfeed, or are they just completely uninformed about the interconnection because the owner didn't file an interconnection application, or ask if he should? I'm wondering...
Ampster
Renewable Energy Hobbyist
Is there a statute or building code requirement that I do not know about?. I have made reasonable inquiries and found none in California. AFAiK the jurisdiction of the Investor Owned Utilities ends at the meter. For sure a building permit is required because an inverter connection is considered a circuit.
Ampster
Renewable Energy Hobbyist
I did a VW conversion in 2011 and then tried to use that pack to power an Outback Radian. I would be happy to discuss the issues if you are interested. The biggest one is voltage. Most EVs more powerful than golf carts run at voltages of 96 volts and up.
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
- Messages
- 19,930
If you are not sending power to the grid, you don't need any agreement.
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
- Messages
- 19,930
Planning for 144v or higher. The inverter battery voltage will be matched to whatever voltage I settle on.
ncsolarelectric
Engineering Support CEO
If your inverter is only drawing power from the grid to power loads and charge batteries, that's fine. But any inverter that operates with it's "output" in parallel with the utility grid MUST have a signed interconnection agreement with the utility before it can be turned on, regardless if it is programmed not to export. Did you ask the utility like SDG&E or PG&E?
ncsolarelectric
Engineering Support CEO
If the inverter is capable of sending power back to the grid AND the output of the inverter is connected directly to the grid, running in parallel with the grid. Then I'm afraid you do. I have never seen a utility that allows parallel generation without an interconnection agreement. If it is capable of exporting power and simply programmed not to, I'm pretty sure it requires an inspection by the utility to verify it is true. I'd bet money on it if I had any.
Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 21,553
Zero export and utility interactive involve two different issues.
There was a need for zero export in Hawaii because the grid couldn't handle any more UL-1741 PV without being destabilized. Now if the customer actually drew 10W, or exported 10W, it isn't going to matter. They're not exporting 3000W or something.
Utility interactive presents the safety issue, which UL-1741 addresses. If the grid goes down and inverter ends up supporting an island of a couple neighbor's loads, anti-islanding detects that and shuts off.
You're probably correct that inspection is required. In my case 20 years ago, they got a copy of signed off permit and equipment list, and they observed meter operating backwards then going forwards when disconnect operated. But the lineman safety of UL-1741 they took on faith from the equipment list and stickers on equipment.
Non UL listed zero export inverters scare me. If they don't implement UL-1741 anti-islanding, I wouldn't trust the accuracy of their current transformer zero export measurement to prevent backfeed for lineman safety. And then there was one that implemented an electronic suicide cord to feed the house during power outages without a mechanically interlocked breaker.
There was a need for zero export in Hawaii because the grid couldn't handle any more UL-1741 PV without being destabilized. Now if the customer actually drew 10W, or exported 10W, it isn't going to matter. They're not exporting 3000W or something.
Utility interactive presents the safety issue, which UL-1741 addresses. If the grid goes down and inverter ends up supporting an island of a couple neighbor's loads, anti-islanding detects that and shuts off.
You're probably correct that inspection is required. In my case 20 years ago, they got a copy of signed off permit and equipment list, and they observed meter operating backwards then going forwards when disconnect operated. But the lineman safety of UL-1741 they took on faith from the equipment list and stickers on equipment.
Non UL listed zero export inverters scare me. If they don't implement UL-1741 anti-islanding, I wouldn't trust the accuracy of their current transformer zero export measurement to prevent backfeed for lineman safety. And then there was one that implemented an electronic suicide cord to feed the house during power outages without a mechanically interlocked breaker.
robby
Photon Vampire
- Joined
- May 1, 2021
- Messages
- 4,310
I don't want to get rid of the Grid, I think that is a really bad idea.
What I want to do is use almost zero power from them and use them as a backup. Right now it's a pretty sweet deal to keep them around but I suspect in the coming years they will raise that minimum fee so high that I will have to give them the boot.
Ampster
Renewable Energy Hobbyist
Of course I did not ask PG&E. Have you seen the recent BS they are telling the CPUC? I know what their policy is. They want to tax us for using the sun to generate power. I asked you for a statute because I have looked and there is nothing that prohibits me from drying my clothes by the sun or generating electricity by the sun. It is still a free Country and I can do any thing behind the meter as long as I have a building permit.
Last edited:
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
- Messages
- 19,930
I'm also keeping the grid as backup for now. Until my micro grid is complete. Then I'll send it packing. Because I agree that the minimum connection fees are going to increase. As more customers choose alternative options, the utility company will have to make money somehow.
wattmatters
Solar Wizard
I've no dog in this fight and know little about the laws in USA but looking at it from afar it looks to me that if a solar PV system in California falls into the category of being interconnected with the grid, then California Public Utilities Commission Rule 21 applies:
Rule 21 Interconnection
Being "behind the meter" to me isn't sufficient to be free from this provision. If a generation system is operating in parallel with a grid supplied circuit, that would automatically make it an interconnected system subject to the requirements of the PUC (including utility approvals).
If your generation system is supplying circuits which are not/never connected to the grid, then it is not operating in parallel and it wouldn't be an interconnected system.
Certainly it is the case in Australia that any generation system operating in parallel with the grid must have prior approval from the utility to be connected and must be installed by qualified personnel only. There is no DIY for grid-tied solar PV here.
timselectric
If I can do it, you can do it.
- Joined
- Feb 5, 2022
- Messages
- 19,930
California isn't in the US, anymore. It's Its own weird country, where everything causes cancer. lol
Similar threads
